Temperature dependence of circular DNA topological states

Circular double stranded DNA has different topological states which are defined by their linking numbers. Equilibrium distribution of linking numbers can be obtained by closing a linear DNA into a circle by ligase. Using Monte Carlo simulation, we predict the temperature dependence of the linking number distribution of small circular DNAs. Our predictions are based on flexible defect excitations resulted from local melting or unstacking of DNA base pairs. We found that the reduced bending rigidity alone can lead to measurable changes of the variance of linking number distribution of short circular DNAs. If the defect is accompanied by local unwinding, the effect becomes much more prominent. The predictions can be easily investigated in experiments, providing a new method to study the micromechanics of sharply bent DNAs and the thermal stability of specific DNA sequences. Furthermore, the predictions are directly applicable to the studies of binding of DNA distorting proteins that can locally reduce DNA rigidity, form DNA kinks, or introduce local unwinding.Comment: 15 pages in preprint format, 4 figure

Assessment of government supervision on the loss of sea sand resource in China

Illegal mining activities on offshore sands have recently increased dramatically in China owing to the strong demand of the construction industry and restriction of river sand mining. By studying the loss mechanism of marine sand resources, this study proposes a simplified linear programming model to quantitatively analyse the control effects related to resource loss and law enforcement costs. To accurately simulate the effectiveness of law enforcement activity, a set of variables is designed in the model to describe the severity of illegal mining and enforcement skills of the officers. Subsequently, based on different settings of law enforcement capability, the model can not only make reasonable projections for sand losses but also provide a minimum cost solution for marine sand control for government agencies. Finally, various regulatory measurements and suggestions are discussed to improve the effectiveness of the government’s regularisation and cost optimisation for law enforcement

Rotation and alignment of high-jj orbitals in transfermium nuclei

The structure of nuclei with $Z\sim100$ is investigated systematically by the Cranked Shell Model (CSM) with pairing correlations treated by a Particle-Number Conserving (PNC) method. In the PNC method, the particle number is conserved and the Pauli blocking effects are taken into account exactly. By fitting the experimental single-particle spectra in these nuclei, a new set of Nilsson parameters ($\kappa$ and $\mu$) is proposed. The experimental kinematic moments of inertia and the band-head energies are reproduced quite well by the PNC-CSM calculations. The band crossing, the effects of high-$j$ intruder orbitals and deformation are discussed in detail.Comment: To appear in the Proceedings of the International Nuclear Physics Conference (INPC2013), June 2-7, 2013, Florence, Ital

The molecular biological expression of SDF-1 and VEGF in rat diabetic retinopathy and the intervention effect of AMD3100

AIM: To measure the expression of stromal cell derived factor-1(SDF-1)and vascular endothelial growth factor(VEGF)in retina of diabetic rats model at the different stage and explore the inhibitory effect of AMD3100 on the expression of SDF-1 and VEGF mRNA by RT-PCR and Western-Blot test.<p>METHODS: RT-PCR and Western-Blot tests were carried out. In RT-PCR test, 60 adult SD rats were divided into normal group, antagonist group, and diabetes group. After diabetic rat model was induced using streptozotocin and antagonist group and diabetic group were injected intravitreously and postocularly with AMD3100 and PBS respectively. All rats were killed and the retina was extracted. after 1,3,5 months and the HE stain of paraffin sections was used and the expression of SDF-1 and VEGF mRNA were measured with RT-PCR. In Western-Blot test, 18 rats were divided into normal group, diabetes group and four antagonist groups which were using different concentration of AMD3100, and killed after 3 months.<p>RESULTS: SDF-1 and VEGF mRNA were expressed in normal group, antagonist group and diabetes group. At the same age group(1, 3 and 5 months)and among the normal group, antagonist group and diabetes group, the difference of expression of SDF-1 and VEGF mRNA were significant. The expressions in diabetic group were always highest and antagonist group lower than diabetic group. The expression of SDF-1 and VEGF mRNA was increased significantly with the extension of disease. The HE Stain of paraffin sections showed DM group had more cell nucleus which protruded internal limited membranes than normal control group and antagonist group. The Western-Blot test showed in 4 antagonist groups the SDF -1 and VEGF protein expression levels gradually decreased with the increases of SDF-1 antagonist AMD3100 concentration, the difference was significant. When intravitreous injected concentration of AMD3100 increased over 10μg/μL, the expression of SDF-1 and VEGF protein did not change, the difference was not statistically significant<p>CONCLUSION: With the progression of diabetic retinopathy, the expression of VEGF and SDF-1 mRNA in the retinal tissue of diabetic rats increased. The antagonist AMD3100 could reduce the expression of SDF-l, VEGF and inhibit the development of new blood vessels. In a certain concentration range, this inhibitory effect of AMD3100 was dose-dependent

A γ\gamma-ray Quasi-Periodic modulation in the Blazar PKS 0301−-243?

We report a nominally high-confidence $\gamma$-ray quasi-periodic modulation in the blazar PKS 0301$-$243. For this target, we analyze its \emph{Fermi}-LAT Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry, are used to build the $\gamma$-ray light curves. Then both the Lomb-Scargle Periodogram and the Weighted Wavelet Z-transform are applied to the light curves to search for period signals. A quasi-periodicity with a period of $2.1\pm0.3$ yr appears at the significance level of $\sim5\sigma$, although it should be noted that this putative quasi-period variability is seen in a data set barely four times longer. We speculate that this $\gamma$-ray quasi-periodic modulation might be evidence of a binary supermassive black hole.Comment: 9 pages, 8 figures; Accepted for publication in Ap